1. Field of the Invention
The present invention relates to a book binding device that binds papers ejected from a sheet processing unit such as a printer and a copy machine, and more particularly, to a milling unit of a book binding device, which removes a coating material adhered to cutting surfaces of coating sheets before a tape is adhered to the coating sheets so as not to generate any adhesion defect of the tape due to the coating material remaining on the cutting surfaces of the coating sheets during binding of the coating sheets.
2. Discussion of the Related Art
Generally, a sheet processing unit 1, as illustrated in FIG. 1 and FIG. 4, includes a sheet carrying unit 2, a sheet aligning unit 3, a binding product conveying unit 4, a receiving stacker 8, and a binding device 5. If sheets are carried in toward the sheet aligning unit 3 through the sheet carrying unit 2, a predetermined number of sheets are stacked on a tray 16 and then are fed to the binding device 5. Ends of a bunch of the sheets fed to the binding device are aligned based on a sheet aligning plate 21 and then are subjected to binding in a state that the sheets are fixed by a gripper 22.
After the bunch of sheets 20 is moved to the binding device, a binding tape 33 is fed to a tape heating unit 25, and heat is given to the tape fed to the tape heating unit so that an adhesive surface 33a of the tap is adhered to the end of the bunch of sheets 20, whereby a binding process of the bunch of sheets is performed.
The table heating unit 25 of the conventional book binding device, as illustrated in FIG. 3 and FIG. 5, includes a square shaped heater 27 provided to rotate based on a support shaft 13. The square shaped heater 27 includes planes A, B and C orthogonal to one another, wherein the plane B opposes the plane A, and the places C and B are selectively located on a front surface by rotation of the support shaft 13.
Furthermore, it is configured that the distance D1 between the plane B and the support shaft 13 is smaller than the distance D1 between the plane C and the support shaft 13.
In a state that the plane C of the heater 27 is located on the front surface, the tape 33 is fed to a place substantially parallel with the plane A of the heater through a tape feeding unit 15. After the bunch of sheets 20 is moved to an adhesion place of the tape 33 in a state that the bunch of sheets 20 is gripped by a gripper (not shown), the end of the bunch of sheets 20 is tightly adhered to the plane A of the heater 27 together with the tape 33.
If a part of the tape 33 is pressed by the plane A of the heater 27 and adhered to the end of the bunch of sheets 20, the tape feeding unit 15 moves to its original place so as not to disturb the binding process.
The binding process will be described in more detail. As illustrated in step {circle around (1)} of FIG. 5, the tape 33 is pressed onto the plane A of the heated heater 27 and welded to a top end of the bunch of sheets 20.
Subsequently, after the tape feeding unit 15 is moved to its original place, the binding process of the bunch of sheets 20 is performed by the steps of {circle around (2)} descending the bunch of sheets 20 from the heater at a predetermined interval, {circle around (3)} rotating the heater 20 by 90° toward an arrow so that the plane B is located toward the front surface, {circle around (4)} welding the tape 33 to a side of the bunch of sheets 20 by ascending the bunch of sheets 20, which has descended at a predetermined interval, toward the heater 27, to weld the tape 33 to a side of the bunch of sheets 20, {circle around (5)} upwardly moving the bunch of sheets 20 of which side is welded to the tape, and {circle around (6)} rotating the heater 27 to its original place to adhere the other end of the bunch of sheets 20 to the tape 33 by means of heat of the plane B.
However, if the coating sheets are subjected to binding using the aforementioned binding device, a part P where a coating material constituting upper and low coating layers 11a and 11b of the coating sheet 11 is pushed to a lower end layer of the coating sheets by a cutter blade is formed during a cutting process using a cutter. For this reason, a problem occurs in that adhesion between the cutting surface of the coating sheet and the tape is remarkably deteriorated.